The tutorial by Andrico Karoulla outlines a comprehensive guide for publishing multiple Gatsby sites within a monorepo using tools like Lerna, Travis CI, and Vercel. It begins with an explanation of monorepos, which are architectural patterns that organize multiple packages in a single repository to streamline dependency management and code sharing. The guide then details the process of converting a Gatsby application into a monorepo, utilizing Lerna to manage dependencies and share components among packages. The tutorial transitions into setting up a continuous integration (CI) pipeline using Travis CI, which automates testing and builds processes before deploying the site to Vercel, a platform that simplifies Node application deployment. Throughout the tutorial, Karoulla emphasizes the importance of understanding the integration of these technologies on a small scale to effectively apply them to production environments. The guide also includes troubleshooting tips and encourages readers to refer to a finished repository for additional support.